Sergio has maintained its annular-like structure over the pastseveral hours. The eye has expanded to nearly 90 n mi across, andthere is little evidence of convective banding in multiple microwaveoverpasses since 1200 UTC this morning. Dvorak classifications fromTAFB and SAB have decreased since the last advisory, however theUW-CIMSS ADT and SATCON are a little higher, so the initialintensity has been lowered only slightly to 85 kt.

Very little change has been made to the official track or intensityforecasts. Sergio is still forecast to slow down and turn northwardover the next day or so. In fact, the 12 h forecast point ispractically already inside the eye of the hurricane. By Tuesday,one or more shortwave troughs working southward along the westernside of a deep-layer trough centered over the southwestern U.S.should cause Sergio to accelerate northeastward. Interestingly,although the various global models solutions have changed with thisforecast cycle, the consensus has been fairly consistent, so onlyminor adjustments were required to the official track forecast.

Slow weakening is still anticipated over the next few days as Sergiopossibly maintains its annular structure. By mid-week, Sergio willbe moving over progressively cooler waters, and a faster rate ofweakening is likely. The NHC forecast is very similar to theprevious advisory, and is near the IVCN and HCCA intensity consensusaids.

Sergio still has its annular-like structure, but the surroundingconvection is not as strong as earlier today. Dvorak objective andsubjective numbers only support 80 kt at this time. Littlesignificant change in strength is anticipated during the next 12 to24 hours while the waters are still relatively warm. In about 2days, the cyclone should encounter cooler waters, and a weakeningtrend at a faster rate is anticipated. Sergio is forecast to be atropical storm by the time it is approaching the Baja Californiapeninsula.

Sergio is currently embedded within light steering currents andis barely moving toward the northwest at 3 kt. A northward drift isexpected during the next 24 hours, but after that time, a broadmid-level trough is forecast to amplify over the west coast of theU.S., and this flow pattern should force Sergio to recurvenortheastward with increasing forward speed. The track guidance isin remarkably good agreement, basically on top of each other for thenext 3 days, increasing the confidence in the track forecast. Beyond3 days, models are in less agreement, but still bring the cyclonevery near the central portion of the Baja California peninsula in 4days or so. The NHC forecast is not very different from theprevious one and is in the middle of the tight guidance envelope.

Sergio continues to have a large 60 nmi diameter eye with severalmesovorticies within it. Although the cloud pattern is quitesymmetric around the eye, the cloud tops are not very cold, likelydue to some ocean upwelling beneath the hurricane. The Dvorakestimates are largely unchanged from earlier and still support aninitial intensity of 80 kt.

Sergio is now drifting northwestward in weak steering currents. Ashortwave trough is expected to approach Sergio from the north, andthat feature, and a large trough over the southwestern United Statesshould cause Sergio to turn northeastward tonight. This motion withan increase in forward speed is expected through the remainder ofthe week. The models are in good agreement overall, and the NHCtrack forecast lies near the middle of the guidance envelope.Based on this forecast, Sergio is expected to be very near the BajaCalifornia peninsula in about 4 days.

Sergio is expected to hold its strength or weaken only slightlyduring the next day or so while it remains in a favorableatmospheric environment. However, steady weakening is expectedafter that time due to increasing shear, drier air, andprogressively cooler waters along the forecast track. Based on theintensity guidance and environmental conditions, Sergio is expectedto be a tropical storm by the time it nears the Baja Californiapeninsula. The cyclone should weaken quickly once it moves inland.The NHC intensity forecast is an update of the previous one and nearthe HCCA and IVCN guidance.

Recent ASCAT data was very helpful in analyzing the 34- and 50-ktwind radii.

Sergio's structure has remained nearly steady-state for the past 24hours. A solid ring of deep convection surrounds Sergio's gianteye, and there is little evidence of any convective bands. Despiteupwelling that is presumably occuring beneath the slow movinghurricane, cloud tops have actually cooled over the past few hours,and satellite intensity estimates from TAFB and SAB have notchanged. The initial intensity has therefore been held at 80 kt,which also agrees with a 1045 UTC UW-CIMSS SATCON estimate.

As long as Sergio can maintain its annular structure in anenvironment of negligible shear, only very gradual weakening isexpected, despite presumably cooling waters beneath the cycloneassociated with its slow movement. The ECMWF and GFS forecast thatthe shear will begin to increase in about 24 to 36 hours, and thecyclone will also be reaching much cooler waters shortly after thattime. A faster rate of weakening is therefore anticipated beyond48 h, in line with the latest intensity consensus, and Sergio isforecast to be a tropical storm when it approaches northwesternMexico in a few days. The cyclone should weaken quickly afterlandfall, and will likely dissipate over the high terrain ofmainland Mexico, though a 5 day remnant low point is still shownfor continuity purposes.

Sergio is moving very little right now, and the slow motion willlikely continue during the day today. By tonight, a large troughcentered over the southwestern United States will cause thehurricane to accelerate northeastward. The track guidance is ingood agreement on the track of Sergio, although there is still someuncertainty associated with the timing for when Sergio will reachthe west coast of the Baja California peninsula. Only minor changeswere made to the official track forecast, which lies near the middleof the guidance envelope and very close to TVCN.

Sergio still consists almost entirely of a solid ring of deepconvection surrounding a very large eye. A pair of timely ASCATpasses from around 1800 UTC show that the hurricane wind fieldremains very symmetric with a large RMW. Although we wouldn'texpect that instrument to capture the true magnitude of thehurricane's maximum winds, the data does suggest that the winds havedecreased at least a little since this morning. UW-CIMSS SATCONvalues have also decreased, so the initial intensity is loweredslightly to 75 kt.

The hurricane is moving very slowly northward, around 3 kt. Therehas been no change to the reasoning behind the track forecast andSergio should still accelerate northeastward in a day or so,approaching the Baja California peninsula by the end of the week.Nearly all of the models have shifted a little toward the southbeyond 24 h, and the NHC track forecast has been adjusted in thatdirection as well, but now lies just north of the multi-modelconsensus.

In the short-term, Sergio is still forecast to gradually weakenwhile it moves very little and continues to upwell cold waters.Beyond 24 h, the hurricane should reach additional cooler waters tothe north, which should cause additional gradual weakening. Ingeneral, the intensity guidance is forecasting Sergio to maintainits intensity a little longer than previously forecast, so the NHCintensity forecast has been adjusted a little higher at 48 h and72 h. It's worth noting that the hurricane would likely maintainits intensity longer if it moves a little farther south over warmerwaters, and any further adjustments southward to the track forecastcould have implications on the intensity forecast. By Fridayafternoon, the cyclone should have reached the Baja Californiapeninsula and more rapid weakening should follow. Although thelow-level center of Sergio will likely quickly dissipate afterreaching mainland Mexico, its mid-level remnants and moisture willcontinue northeastward, potentially causing heavy rainfall acrossparts of the southwestern United States.

Conventional satellite visible and enhanced BD-curve infraredimagery reveal a rather large, curved band feature outliningabout 90 percent of what once was an enclosed ragged eye. Thisprimary band is still producing very cold cloud tops, and thesatellite intensity estimates have changed little, so the initialintensity will be held at 75 kt for this advisory.

Sergio should very slowly spin down during the next 36 hours as ittraverses marginally conducive oceanic temperatures. Beyond thatperiod, Sergio should enter a region of much cooler sea surfacetemperatures and increasing southwesterly shear, which should inducefurther weakening and at a faster rate. Toward the end of the week,Sergio is forecast to move inland over the central Baja Californiapeninsula and into northernwestern Mexico in 4 days. At which time,the cyclone will quickly weaken and degenerate into a remnant lowover the southwestern United States. Moisture associated with theremnants of Sergio is expected to affect northwestern Mexico andportions of the southwest United States over the weekend and couldpotentially cause heavy rainfall in this region. For moreinformation about this potential hazard, see products from theWeather Prediction Center and your local NWS forecast office.

The initial motion is estimated to be northward, or 360/3 kt.Sergio should begin accelerating northeastward Tuesday, andapproach the central Baja California peninsula in about 3 days.The NHC forecast is basically an update of the previous one and isclose to the various multi-model consensus aids.

Sergio's cloud pattern has changed little in the past 6 hours and iscomprised of a fragmented, large outer ring, about 100 n mi indiameter. The coldest cloud tops are now confined to just thesoutheast portion of cyclone's circulation. The Dvorak satelliteintensity estimates from TAFB and SAB support maintaining theinitial intensity at 75 kt.

Some slow weakening, or possibly very little change in strength, isexpected during the next 36 hours as Sergio traverses marginallyconducive oceanic temperatures and remains in a low shearsurrounding environment. Afterward, the cyclone should enter aregion of much cooler sea surface temperatures and increasingsouthwesterly shear, which should influence significant weakeningand reducing Sergio to a tropical storm prior to landfall. Sergiois forecast to move inland over Baja California Sur on Friday andinto the northwestern Mexico state of Sonora early Saturday. Atthe end of the forecast period, Sergio is expected to furtherdegenerate into a remnant low over the southwestern United States.The intensity forecast is weighed heavily on the NOAA-HCCA and theGFS and ECMWF global models which show Sergio making landfall as atropical storm.

Moisture associated with the remnants of Sergio is expected toaffect northwestern Mexico and portions of the southwest UnitedStates over the weekend and could potentially cause heavy rainfallin this region. For more information about this potential hazard,see products from the Weather Prediction Center and your local NWSforecast office.

The initial motion is estimated to be northeastward, or 050/5 kt.Sergio should begin accelerating in the aforementioned directionthis morning, and approach the central Baja California peninsula inabout 3 days. There is high confidence in the forecast track as theavailable global and regional models are clustered tightly togetherthrough day 5. The NHC forecast lies in the middle of the guidancecluster and is close to the TVCN/HCCA consensus models.

Sergio appears to have resumed its slow weakening. Cloud tops onthe western half of the hurricane have warmed, and Dvorakclassifications from TAFB and SAB have decreased. However, recentAMSR-2 and SSMIS images indicate that the hurricane still has alarge but well-defined inner-core in the low and mid-levels. Theinitial intensity is set at 70 kt, based on a blend of Final-T andCI numbers from TAFB and SAB, and the most recent UW-CIMSS SATCONestimate.

There has been almost no change to the intensity forecast and onlyvery gradual weakening is forecast during the next 36 to 48 h.Beyond that time, Sergio will pass over colder SSTs, including thestill-present cold wake of former Hurricane Rosa, and continuedweakening is expected as the cyclone approaches the BajaCalifornia peninsula. Sergio is therefore still forecast to be atropical storm when it reaches the west coast of the Baja Californiapeninsula in a few days. Rapid weakening is likely after Sergiomakes its final landfall in northwestern mainland Mexico late thisweek, and the cyclone will likely dissipate or become a remnant lowshortly after moving inland.

Virtually no change has been made to the track forecast, whichremains near the TVCN and HCCA consensus aids. All of the globaland regional models show that Sergio will accelerate generallynortheastward for the next 3 days, approaching the Baja Californiapeninsula on Friday. There is still some disagreement among themodels regarding the exact speed of Sergio through that time, butthere is very little cross-track spread. Confidence in the trackforecast is fairly high.

Moisture associated with the remnants of Sergio is expected toaffect portions of northwestern Mexico, the southwestern UnitedStates, and the U.S. southern plains over the weekend and couldpotentially cause heavy rainfall in this region. For moreinformation about this potential hazard, see products from theWeather Prediction Center and your local NWS forecast office.

The GOES-15 satellite presentation and an earlier ATMS polarorbiter microwave image revealed little change in Sergio's cloudpattern during the past 6 hours. Deep convection persists in thenorth semicircle in the form of a rather large curved band while thesouthern portion is comprised of fragmented bands. A blend of theDvorak satellite classifications, which haven't changed much,supports holding the initial intensity at 60 kt for this advisory.

Very little change in strength is forecast during the next 6-12hours, as Sergio traverses relatively warm oceanic temperatures andremains in a low shear surrounding environment. Afterward,statistical and dynamical intensity guidance shows weakening throughthe 48 period, or prior to landfall, as the cyclone moves overcooler waters and into a region of increasing southwesterly verticalshear. Over the weekend, after quickly moving over Baja CaliforniaSur, Sergio will weaken further over the state of Sonora innorthwestern Mexico, degenerate into a remnant low by day 4, anddissipate over the Southern Plains of the United States.

The initial motion is estimated to be east-northeastward, or 060/10kt, within the deep-layer southwesterly flow produced by amid-latitude trough stretching southwestward over the easternPacific from the southwestern United States. Sergio should continueto accelerate toward the east-northeast or northeast over the nextfew days, moving over Baja California Sur on Friday, and over theGulf of California and into northwestern Mexico Friday night andSaturday.

The primary threat associated with Sergio and its remnants willlikely be life-threatening flash flooding and mudslides withinmountainous terrain in the Mexico state of Sonora, the U.S.Southern Plains and the Ozarks through the weekend. For moreinformation about this potential hazard, see products from theWeather Prediction Center and your local weather forecast office.

The organization of the cloud pattern has remained unchanged duringthe day, except that the deep convection has continued to weaken.Nevertheless, Dvorak numbers from TAFB and SAB still support aninitial intensity of 55 kt. Some fluctuations in intensity arelikely during the next 12 hours while the cyclone is over relativelywarm waters and is embedded in a low shear environment. Since bothof these factors will become unfavorable in about 12 to 24 hours,the NHC forecast calls for weakening. Sergio, however, is expectedto still be a tropical storm by the time it approaches the BajaCalifornia peninsula. After that time, Sergio will move overmainland Mexico and weaken much faster.

Sergio is moving toward the northeast or 050 degrees at 12 kt. Thecyclone is embedded within the southwesterly winds associatedwith a large mid-latitude trough, and this flow pattern willcontinue to steer Sergio toward the northeast with an increase inforward speed. The forecast track brings the center of a weakenedSergio over the central portion of the Baja California peninsula inabout a day and half, but winds will reach the coast a little bitearlier. Track models continue to be in very good agreement, andconsequently the guidance envelope is quite tight. The NHC forecastremains unchanged and is in the middle of the guidance envelope.

The primary threat associated with Sergio and its remnants continuesto be life-threatening flash flooding and mudslides withinmountainous terrain in the Mexico states of Baja California Sur,Sonora, the U.S. Southern Plains, and the Ozarks through theweekend. For more information about this potential hazard, seeproducts from the Weather Prediction Center and your local weatherforecast office.

This evening's satellite presentation depicts a rather ragged andelongated banding eye-like feature with fragmented curved bandsencircling the periphery of cyclone. The subjective intensityestimates from TAFB and SAB, however, still yield an initialintensity of 55 kt.

The UW-CIMSS shear analysis shows that the westerly shear hasincreased to 15-20 kt, and the Decay-SHIPS as well as the globalmodels indicate that the shear magnitude will increase further tonear 50 kt prior to landfall. This inhibiting upper wind patternalong with slightly cooler oceanic temperatures should influencesome further weakening as it approaches the Baja Californiapeninsula. Sergio is forecast to move inland over Baja CaliforniaSur on Friday and into the northwestern Mexico state of Sonora earlySaturday as a depression. At the end of the forecast period, Sergiois expected to further degenerate into a post-tropical weak low overthe southwestern United States. The intensity forecast is based onthe NOAA-HCCA, and the GFS/ECMWF global models which show Sergiomaking landfall Friday as a tropical storm.

The initial motion is estimated to be northeastward, or 050/14 kt,and this general motion is forecast through the entire 72 hourperiod with a continued increase in forward speed. Sergio will beapproaching the central Baja California peninsula Friday, althoughthe tropical-storm-force winds are likely to arrive Thursday night.There is continued high confidence in the forecast track as theavailable large-scale and hurricane models are clustered tightlytogether through 72 hours. The NHC forecast lies in the middle ofthe guidance cluster and is close to the TVCN/HCCA consensus models.

The primary threat associated with Sergio and its remnants continuesto be life-threatening flash flooding and mudslides withinmountainous terrain in the Mexico states of Baja California Sur,Sonora, the U.S. Southern Plains, and the Ozarks through theweekend. For more information about this potential hazard, seeproducts from the Weather Prediction Center and your local weatherforecast office.

Sergio's cloud pattern has changed little during the past severalhours, and the Dvorak satellite intensity estimates from TAFB andSAB haven't changed either. A partial ASCAT-B scatterometer passrevealed numerous 45-kt winds and a 50-kt northerly wind in thecoldest cloud tops of the curved band wrapping around the northportion of the circulation. Based on these data, the initialintensity is held at 55 kt for this advisory.

The intensity forecast philosophy remains unchanged. A combinationof increasing southwesterly shear, a drier and more stablesurrounding environment, and slightly cooler oceanic temperaturesshould influence some weakening as it approaches the Baja Californiapeninsula. The cyclone is expected to move inland overBaja California Sur on Friday and into the northwestern Mexico stateof Sonora early Saturday. Afterward, rapid weakening, andultimately dissipation, is expected after Sergio makes its secondlandfall along the coast of the mainland Mexico. A 72 hourpost-tropical/remnant low point is maintained to simply representthe inland motion of Sergio. The intensity forecast is onceagain based on the NOAA-HCCA, and the GFS/ECMWF global models, whichshow Sergio making landfall Friday as a tropical storm.

The initial motion is estimated to be northeastward, or 050/15kt, within the deep-layer southwesterly flow produced by amid-latitude trough stretching southwestward over the easternPacific from the southwestern United States. Sergio should continuemoving in this general motion through the entire 72 hour period witha continued increase in forward speed. Sergio will be approachingthe central Baja California peninsula Friday, although thetropical-storm-force winds are likely to arrive Thursday night.The NHC forecast lies in the middle of the tightly clusteredguidance and is close to the multi-model consensus aids.

The primary threat associated with Sergio and its remnants continuesto be life-threatening flash flooding and mudslides withinmountainous terrain in the Mexico states of Baja California Sur,Sonora, the U.S. Southern Plains, and the Ozarks through theweekend. For more information about this potential hazard, seeproducts from the Weather Prediction Center and your local weatherforecast office.